Borrowed Funds (Details) (USD $)								6 Months Ended		6 Months Ended				6 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Apr. 30, 2012 First American Equipment Finance	Jun. 30, 2012 5.125% Senior Notes Due February 2013 City National Corporation	Dec. 31, 2011 5.125% Senior Notes Due February 2013 City National Corporation	Jun. 30, 2012 5.25% Senior Notes Due September 2020 City National Corporation	Dec. 31, 2011 5.25% Senior Notes Due September 2020 City National Corporation	Jun. 30, 2012 9.00% Subordinated Notes Due July 2019 City National Bank Y	Dec. 31, 2011 9.00% Subordinated Notes Due July 2019 City National Bank	Jun. 30, 2012 9.00% Subordinated Notes Due July 2019 City National Bank LIBOR	Jun. 30, 2012 9.00% Subordinated Notes Due July 2019 City National Bank Prime rate	Jun. 30, 2012 9.00% Subordinated Notes Due August 2019 City National Bank	Dec. 31, 2011 9.00% Subordinated Notes Due August 2019 City National Bank	Jun. 30, 2012 Fixed and Floating Subordinated Notes due August 2019 City National Bank Y	Dec. 31, 2011 Fixed and Floating Subordinated Notes due August 2019 City National Bank	Jun. 30, 2012 5.375% Subordinated Notes Due July 2022 City National Bank	Jun. 30, 2012 Floating Rate Securities Due November 2034 Business Bancorp Capital Trust I	Dec. 31, 2011 Floating Rate Securities Due November 2034 Business Bancorp Capital Trust I	Jun. 30, 2012 Nonrecourse debt	Jun. 30, 2012 Nonrecourse debt First American Equipment Finance	Apr. 30, 2012 Nonrecourse debt First American Equipment Finance
Short-term borrowings
Current portion of senior notes				$ 210,466,000
Federal funds purchased	110,000,000	50,000,000
Total short-term borrowings	322,077,000	50,000,000																	1,611,000
Long-term debt
Long-term debt	712,280,000	697,778,000			215,848,000	297,461,000	297,308,000	49,736,000	49,718,000			74,867,000	74,858,000	54,902,000	54,895,000	149,018,000	5,151,000	5,151,000	81,145,000
Borrowings and nonrecourse debt			320,900,000
Borrowings and nonrecourse debt																				82,800,000	320,900,000
Long-term debt excluding discount and cost of issuance																$ 150,000,000
Fixed interest rate (as a percent)				5.125%	5.125%	5.25%	5.25%	9.00%	9.00%			9.00%	9.00%			5.375%
Average interest rate (as a percent)																			4.09%
Variable rate basis										LIBOR	Prime rate			three-month LIBOR			three-month LIBOR
Frequency to reset interest rate														Quarterly			Quarterly
Interest rate cap (as a percent)														10.00%
Interest rate for initial period (as a percent)								9.00%						9.00%
Initial interest rate period (in years)								5						5
Basis spread after initial period (as a percent)										6.00%	5.00%			6.00%
Basis spread (as a percent)																	1.965%
Interest rate as of reporting date (as a percent)																	2.43%